Double pointed injection needle

ABSTRACT

A disposable double pointed injection needle has a needle hub to which a thin needle cannula is permanently fasten and which needle hub can be mounted on to a syringe comprising a dose setting and injection mechanism and a cartridge containing a liquid medicine to be injected subcutaneously into a human body. The needle hub is provided with a safety shield guided on the outside surface of the needle hub. The safety shield is urged in a direction away from the needle hub by a spring located between the needle hub and the safety shield. The safety shield has a number of protrusions guided in guiding tracks on the outside surface of the needle hub. The guiding tracks are designed such that the safety shield during injection is moved towards the needle hub, and after injection is moved away from the needle hub by the spring and locked in an irreversible position where the safety shield covers the needle cannula and prevents accidental needle stick injuries.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims priority under 35 U.S.C. §119 based onU.S. provisional patent application No. 60/254,051, filed on Dec. 7,2000.

BACKGROUND OF THE INVENTION

The invention relates to a disposable double pointed injection needlehaving an injection part with a skin piercing end and a cartridge partfor inserting into a cartridge containing a liquid medicine to beinjected subcutaneously. The cannula of the injection needle is fastenedin a needle hub for mounting on a syringe, which syringe supports thecartridge into which the cartridge part of the injection needlepenetrates.

The invention further relates to an insulin injection system comprisinga pen shaped syringe supporting a cartridge with insulin, a dose settingand injection mechanism and a disposable double pointed injectionneedle.

Injections where a liquid is expelled into the human body are usuallyperformed either as intramuscular injections i.e. injections into themuscle tissue, or as subcutaneously injections i.e. injections into thesubcutaneous tissue lying between the cutis and the muscle tissue.

When performing intramuscular injections of a vaccine it is according toBritish Medical Journal, volume 321, p. 931, important to use longinjections needles in order to avoid local reactions such as redness andswelling. According to the article, use of injection needles having alength of 25 mm reduced the rate of local reaction significantlycompared to an injection needle having a length of 16 mm.

Long injection needles must have a relatively large diameter in ordernot to break during injection. The injection needles referred to in theabove mentioned article has a diameter of 23 G for the 25 mm longinjection needle and 25 G for the 16 mm long injection needle.

The outside diameters of injection needles are indicated by a “G” and agauge number increasing with thinner needles. Thus the outside diameterof a G 23 is 0.60 mm and of a G 25 0.50 mm.

It has for some years been known to provide long injection needles withsafety protective devices in order to prevent accidental needle stickinjuries. Such safety protective devices are e.g. known from EP 409.180and U.S. Pat. No. 4.813.940. These known safety protective devicescomprises a number of telescopic sleeves, which telescopic sleevesslides into each other in order to expose an injection needle covered bythe telescopic sleeves when not in use. The injection needles used hasopposite the skin piercing end a needle connector for connecting theinjection needle with an ordinary hypodermic syringe. By the expression“ordinary hypodermic syringe” is meant a syringe of the type where themedicine to be injected is drawn from a vial into the syringe prior toeach injection. In practical use the medicine has to flow through theinjection needle twice for every injection when using such an ordinaryhypodermic syringe, but due to the large diameter and the large bore ofa long injection needle clogging is not a problem.

U.S. Pat. No. 5.429.612 discloses yet another long injection needlehaving a safety protective sleeve which can be moved into a positionwhere the safety protective sleeve covers the injection part of theneedle cannula. As can be seen in FIG. 1 of U.S. Pat. No. 5.429.612 theinjection part of the needle cannula has a length, which makes itnecessary to support the needle cannula by at least one disk 21. Thesyringe is loaded with a flask containing the medicament to be injected.Since the syringe has no dose setting and injection mechanism like theones known from insulin injection pens, the entire content of the flaskis emptied into the patient in one injection, which is the usualprocedure when injecting anaesthesia in dentistry. When using theembodiments shown in FIGS. 2 and 3, the user must manually rotate theshield after use in order to bring the tongue 26 from the first track 23and into the second track 24. Doing so the user is exposed to a greatdanger, since the rotation must be done after the contaminated needlecannula has been retracted from the body of the patient.

When providing long injection needle with safety protective sleevesthere are hardly any limitation to the length of the injection needle aslong as the relationship between the length and the diameter issufficient to prevent unwanted needle breakage. The muscular tissue isin a human body normally located approximately 10 to 14 mm below thesurface of the skin. The part of a long injection needle entering thehuman body therefore has to be at least 14 mm in order to reach into themuscular tissue of the human body. As can be seen from the prior artinjection needles, the length of the needle cannula from its fasteningspoint in the needle connector to its skin piercing end is substantiallylonger than the part of the needle cannula, which enters the human bodyduring injection. This presents however no problem since these needlehas a large diameter sufficient to withstand breakage.

Some medicines however has to be injected subcutaneously i.e. in thesubcutis lying between the cutis and a muscle membrane which cover theunderlying muscles. If for instead insulin for treating diabetes isinjected into the muscle tissue it will be absorbed in the body toquickly and an unwanted drop in the blood sugar may be the result. Inorder to prevent intramuscular injection of insulin it is quite commonfor people suffering from diabetes to inject into a lifted skin fold. Itis however becoming more and more preferred by diabetic persons toinject directly at an angle of 90° without the skin fold, using an extrashort needle. The extra short needle must have an overall length of theinjection part of the needle cannula short enough to avoid intramuscularinjections. Such extra short needles are e.g. known from WO 97.23253,which discloses an injection needle having an overall length of theinjection part laying in the interval 4 to 6 mm.

Very short injection needle are not subject to breakage in the samedegree as long injection needles, and can therefore be made with a muchsmaller diameter. WO 93.00948 reveals a short injection needle, havingan injection part in the interval 8 to 12 mm, for injecting insulin. Thediameter of the needle cannula is thinner than G 29. Such short and thinneedles cannot be used in connection with an ordinary hypodermic syringewhere the medicine is drawn up from a vial prior to each injection sincethis requires the medicine to flow through the needle twice for everyinjection, which can result in clogging of the bore of the injectionneedle, especially if the medicine is a suspension. However when theshort and thin needle are used in connection with a syringe supporting acartridge containing the medicine to be injected, the medicine only hasto flow through the injection needle once which in itself halves therisk of clogging, and thereby allows very thin injection needles to beused. At the same time, when an injection needle has only a smalldiameter both outside and inside, the pressure needed to force a liquidthrough the bore of the injection needle is high when the injectionneedle is long, but substantially smaller if the injection needle isshort.

SUMMARY OF THE INVENTION

These known short and thin injection needles are however not providedwith any safety protective devices, while the safety protective sleevesknown from the prior art would permanently cover a large part of theinjection part of the injection needle thereby preventing a shortinjection needle from penetrating through the cutis layer, which layerusually is between 2 to 3 mm thick, and into the subcutis layer of ahuman body.

Injection needles with relatively thin diameter and with a length of theinjection part of the needle cannula between 4 to 12 mm are often usedfor self-injection of insulin i.e. where the patient injects him orherself. However for self-injection in private settings, safetyprotective devices providing safety against accidental needle stickinjuries are not considered to be important, since no other personbeside the patient performing the self-injection has contact with theinjection needle. Safety protective devices providing safety againstaccidental needle stick injuries would however be preferred in domesticresidences if other people, and especially children, are present in thedomestic residence.

It is however very important in hospital settings where many peopleinteracts to use injection needles, which are provided with some kind ofsafety protective device preventing accidental needle stick injuries.All the prior art injection needles provided with safety protectivedevices are long injection needles for intramuscular injections. Theselong injection needles are often of the type used on traditionalhypodermic syringes where the medicine has to flow through the bore ofthe needle twice for every injection thereby limiting the minimumdiameter of the bore and the outside diameter of the injection needle.Hospitalised people suffering from diabetes are usually injected withthese long injection needles having a relatively large outside diameter.This is also the case with senior citizens in retirement homes, withchildren in schools and in day-care facilities, in fact every place aninsulin injection is performed by a professional health care worker longinjection needles are used, since they are the only ones providingsufficient safety for the health care worker. The health care workergiving the injection using a long needle has to be very careful only topenetrate into the subcutis layer in order for the insulin to becorrectly absorbed in the human body, and at the same time the largediameter of a long injection needle gives the patient a high painperception. No matter how careful health care workers are when injectinginsulin, the insulin will sometimes unintended be injected into themuscle tissue, with the subsequent changes in insulin absorption anddiabetes control. Patients which are newly diagnosed with diabetes andnot familiar with self-injection often finds a long injection needlewith a large diameter very intimidating, which is also the case withchildren. At the same time needles with large diameters tends tofracture the skin more than thin needles.

It is an object of the present invention is to provide a short and thindisposable double pointed injection needle for subcutaneously injection,which overcomes the deficiencies of the prior art. It is further anobject to provide a short and thin disposable double pointed injectionneedle which is equipped with a safety protective device preventingaccidental needle stick injuries, and which injection needle could beused on a modern type syringe supporting a cartridge containing a liquidmedicine.

This is obtained by a disposable double pointed injection needleaccording to claim 1.

The short and thin injection needle is provided with a movable needleprotector which allows normal use of the injection needle duringinjection, and which movable needle protector once the injection is donecan be shifted manually or automatically into a position where themovable needle protector covers the skin piercing end of the needlecannula in an irreversible manner. When the skin-piercing end of thecannula is covered, the injection needle can be removed from the syringeand disposed off without endangering the people performing the injectionand the people disposing of the used injection needles. The cartridgepart of the needle cannula is permanently covered by the hub preventingthe cartridge part of the needle cannula from accidental penetrating theskin of the persons handling the injection needle.

Hospitalised people suffering from diabetes or a similar disease ishereby provided with a disposable double pointed injection needle whichonly penetrates into the subcutis layer of the human body duringinjection and which at the same time offers sufficient protectionagainst accidental needle sticks. This will relieve the patients fromthe variations in the depth of penetration occurring when injections aregiven using long injection needles and provide safety for the healthcare workers at the same time. Since the disposable double pointedinjection needle is both short and thin, the pain perception will bevery low.

Since especially children are very sensible to the appearance of theinjection needle, a short disposable double pointed injection needlewhere a major part of the injection part of the needle cannula is hiddeninside the boundaries of a safety shield prior to injection will make itpsychologically easier for a child to accept the fact that dailyinjections of a liquid medicament such as insulin or growth hormone isneeded.

When as disclosed in claim 2, the movable needle protector is acylinder-shaped safety shield surrounding at least the major part of theinjection part of the needle cannula when the needle cannula is in anunused state, and which cylinder-shaped safety shield can belongitudinal moved relatively to the needle cannula, such that thesafety shield is first moved in the proximal direction when theinjection part of the cannula is penetrated into the subcutis layer of ahuman body, thereby exposing the major part of the injection part to thehuman body, and which safety shield automatically moves in the distaldirection until the cannula is fully surrounded by the safety shieldwhen the injection part of said cannula is removed from the subcutislayer of a human body, it is ensured that the entire injection part ofthe needle cannula is securely covered at all times during theinjection.

In a preferred embodiment of the disposable double pointed injectionneedle according to the invention the safety shield is automaticallymoved in the distal direction when the injection part of the cannula isremoved from the subcutis layer of the human body by a resilient elementsuch as a helical spring, which resilient element is located between theneedle hub and the safety shield, and which resilient element is tightenwhen the injection part of said cannula is penetrated into the subcutislayer of the human body. Such an automatic movement by a spring oranother resilient element ensures that the shield is always moved intothe position where its covers the injection part of the needle cannulawithout the need of the user to manually push the shield into thisposition. Any type of resilient element can be utilized, although it ispreferred to use a helical spring. Such a helical spring can be eithermetallic or made from a polymeric material.

When as disclosed in claim 4, the safety shield is guided on the outsidesurface of the needle hub, it is ensured that the safety shield can bepushed all the way back such that a major part of the injection part ofthe needle cannula of the injection needle is exposed to the human bodyduring injection thereby limiting the overall length of the needlecannula of the injection needle.

When, as disclosed in claim 5, the safety shield is provided with anumber of inwardly pointed projections guided in guiding tracks providedon the external surface of the needle hub, it is ensured that the shieldmoves relatively to the needle cannula and the needle hub in apredetermined pattern.

In yet a preferred embodiment of the disposable double pointed injectionneedle according to the invention at least two guiding tracks arelocated opposite each other on the needle hub each comprises a firstpart being substantially parallel to the needle cannula and a secondpart being connected to the first part at an acute angle. Two, three ormore guiding tracks provide stability to the shield, and an acute anglebetween the two parts of each track provides a smooth movement of theshield.

When, as disclosed in claim 7, one of the parts of the guiding tracks isopen at the distal end of the needle hub allowing the projections toenter each guiding track, and that the open part of each guiding trackat the distal end is provided with an elevation, it is ensured that theprojections are easily inserted in the tracks, and that once located inthe guiding tracks is prevented from sliding out of grip with theguiding track. The part of the guiding tracks being open at the distalend can either be the first part or the second part.

In another embodiment of the disposable double pointed injection needleaccording to the invention, each projection can be shifted between threedifferent locations in the guiding track:

a first location where the safety shield surrounds at least the majorpart of the injection part of said cannula, and in which location saidneedle cannula is in an unused state

a second location where the major part of the injection part is exposedto the human body, and in which location the needle cannula ispenetrated into the human body, and

a third location where the safety shield fully surrounds the injectionpart of the cannula, and in which location the cannula is fully removedfrom the human body.

By having the projections and the shield move relatively to the needlehub in the pattern described in claim 8, it is ensured that the majorpart of the needle cannula extending in the distal direction from theneedle hub is inserted into the human body during injection.

When, as disclosed in claim 9, at least one of the guiding track has atleast one elevation with a steep front preventing the projection frommoving backwards in the guiding track when the projection has enteredthe second or/and the third position, it is ensured that the safetyshield can not be moved in the backward direction once an injection hascommenced

When, as disclosed in claim 10, one of the elevations is formed as ahole or a well located at the end of one of the guiding tracks near tothe distal top end of the needle hub, and the projection drops into thehole or well when the projection is in the third location, such that thesafety shield is irreversible locked to the needle hub when said cannulais fully removed from the human body, it is ensured that the safetyshield is irreversible locked to the needle hub when the needle cannulais fully removed from the human body thereby preventing reuse of saidinjection needle.

When, as disclosed in claim 11, the disposable double pointed injectionneedle further comprises a container surrounding the needle hub, theneedle cannula, the resilient element and the safety shield, and whichcontainer has inwardly pointing ribs engaging similar outwards pointingribs on the needle hub, it is ensured that the rotational force emergingwhen the container is rotated is transferred to the needle hub.

It is also an object of the present invention to provide a pen basedinsulin injection system, which can be used in hospital settings orother public places without exposing the professional people working inthese places to accidental needle stick injuries.

This is obtained by an insulin injection system according to claim 12.

By having a complete system comprising both a pen shaped syringesupporting a cartridge and a short and thin safety engineered injectionneedle with a needle protector, a complete pen based injection systemfor the treatment of diabetes can now be used in hospitals only usingneedle-based medical devices designed to provide health care workerswith additional protection against accidental needle stick injuries andpotential exposure to infectious diseases.

In one embodiment of the disposable double pointed injection needleaccording to the invention the injection needle is further provided withmeans providing the user with a visual indication when the injectionneedle is in a potentially unsafe position. In another embodiment of thedisposable double pointed injection needle according to the inventionthe injection needle is further provided with means providing the userwith a visual indication when said disposable double pointed injectionneedle is in a potentially safe position. As the disposable doublepointed injection needle according to the invention has previously beendescribed it is somewhat difficult for the user to visible inspect ifthe disposable double pointed injection needle has been used. Thisproblem is overcome by providing the disposable double pointed injectionneedle with means according to claim 13 and/or 14.

When, as disclosed in claim 15, the means providing the user with avisual indications comprises at least one transparent area in themovable needle protector and at least one first area and/or at least onesecond area located on the outside surface of the needle hub, and asdisclosed in claim 16, the first areas located on the outside surface ofthe needle hub is visible through the transparent areas when theprojection is in the first location, and/or that said second areaslocated on the outside surface of the needle hub is visible through thetransparent areas in said movable needle protector when the projectionis locked in said third location, it becomes very simple for an user toinspect whether the disposable double pointed injection needle is unusedor not.

When, as disclosed in claim 17, the first areas and/or the second areasare provided with different colours or symbols, it is ensured that evenusers with poor sight can visible inspect whether the disposable doublepointed injection needle has been used or not.

In the present context, the term ‘injection’ is taken to mean expellinga liquid along a hollow needle or another hollow conduit and into ahuman body, in which human body a part of the hollow needle or conduitis temporarily inserted.

Although the wording “human body” is used through out this application,the disposable double pointed injection needle claimed could as well beused on any mammal body without dispersing from the scope of the claims.

In the present context, the term “cartridge” is taken to mean a hollowtube-like container having one end permanently sealed by a membrane,which membrane is penetrated by the cartridge part of the needle cannulawhen the double pointed injection needle is attached to the cartridge orthe syringe. The other end of the cartridge is a displaceable plate orcylinder that fits tightly against the inner walls of the cartridge. Adiscrete dose is expelled through the double pointed injection needleattached to the cartridge or the syringe if the plate or cylinder isdisplaced in the direction towards the permanent membrane penetrated bythe cartridge part of the double pointed injection needle.

The cartridge containing the medicine is usually supported in the distalend of the housing of the syringe. The cartridge can either bepermanently fastened in the housing or it can be exchangeable. If thecartridge is permanently fastened in the housing, the entire syringe isdisposed of when the cartridge is empty, but if the cartridge isexchangeable then only the empty cartridge is disposed of and a new,full cartridge is loaded into the housing of the syringe.

It is to be understood that the wording “pen shaped syringe”, usedthroughout this application, merely refers to a syringe having an oblongor elongated shape and which fits into one hand, somewhat like a pen forwriting. Although such writing pens usually have a tubularcross-section, modern writing pens often have a different cross-sectionsuch as triangular, rectangular or square. Pen shaped syringes can in asimilar way have a large variety of different cross-sections.

When referring to the disposable double pointed injection needleaccording to the present application the term “relatively thin outsidediameter” is taken to mean a needle cannula having an outside diameterthinner than G28. The use of G28 needle cannulas for injecting insulinhas for many years been widely accepted as the standard size, and G29 orthinner needle cannulas are therefore often referred to as “thininjection needles”. The needle cannula of the disposable double pointedinjection needle can be as thin as 31G or even 32G.

A “G” and a gauge number increasing with thinner needles indicate theoutside diameter of the needle cannula. The following table indicatesthe relation between the gauge number and the outside diameter of theneedle cannula, for the gauge numbers referred to in the presentapplication.

Gauge: 23 G 25 G 27 G 29 G 30 G 31 G 32 G Diameter: 0,60 0,50 mm 0,400,33 0,30 0,25 mm 0,23 mm mm mm mm mm

The part of the needle cannula referred to as the “cartridge part” isthe part entering the cartridge. which is to be understood as the partextending in the proximal direction from its fastening point in theneedle hub, while the part referred to as the “injection part” of theneedle cannula is the part entering the human body during injection,which is to be understood as the part extending in the proximaldirection from its fastenings point in the needle hub. The injectionpart extending in the proximal direction from its fastening point in theneedle hub is often a little longer than the part actually penetratinginto the human body. The length different between the injection part andthe part actually penetrating into the human body depends on the heightof the hub tower and the wall thickness of the top surface of the safetyshield. Usually the part of the needle cannula, which penetrates intothe human body has a length between 4 to 12 mm, such that the depth ofpenetration lies between 4 to 12 mm.

In the present context, the term “dose setting and injection mechanism”is taken to mean a mechanism by which a desired dose of a liquidmedicine contained in a cartridge can first be set and later injected,leaving the remaining part of the liquid medicine in the cartridge. Themechanism can either be mechanical or electronic, or both. The injectionis usually done by having a mechanical element pressing forward theplate or cylinder inside the cartridge in correspondence with the setdose. The force used for driving forward this mechanical element ispreferably delivered either physically by the user or by an electricalmotor.

In the present context, the term “subcutaneously” refers to the subcutislayer of the human body, which are the layer located between the cutisand a muscle membrane covering the muscular tissue. By a number ofmeasurements it is found that the average depth of the muscle membraneis 9.5 mm for males and 13.8 for females, measured from the outside ofthe human skin. Recognizing that the emission of liquid from aninjection needle, due to the oblique cut end of the skin piercing end ofthe needle cannula, takes place in a distance from the skin piercing endin the range 0.4 to 1.2 mm, an injection needle for subcutaneouslyinjections should preferably have an length of the part penetrating intothe subcutaneous layer shorter than approximately 10 mm. Although aninjection needle having a length of this part, which equals the depth ofpenetration, up to approximately 14 mm would be acceptable for females.In order to ensure penetration of the cutis of a human being, theminimum length of the part of the needle cannula penetrating thesubcutaneous layer must be longer than approximately 4 mm.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

The invention will be explained more fully below in connection with apreferred embodiment and with reference to the drawings in which:

FIG. 1 Shows an exploded view of the disposable double pointed injectionneedle according to the invention.

FIG. 2 Shows a sectional view of the disposable double pointed injectionneedle according to the invention.

FIG. 3 Shows a sectional view of the safety shield according to anembodiment of the invention.

FIG. 4 Shows a sectional view of the needle hub according to anembodiment of the invention.

FIG. 5 Shows a sectional view of the top of the safety shield and of theskin-piercing end of the needle cannula.

FIG. 6 Shows a perspective view of the needle hub according to anembodiment of the invention.

FIG. 7 Shows a perspective view of the disposable double pointedinjection needle with the visual indication showing that the disposabledouble pointed injection needle is in an unlocked position.

FIG. 8 Shows a perspective view of the disposable double pointedinjection needle with the visual indication showing that the disposabledouble pointed injection needle is in a locked position.

The figures are schematic and simplified for clarity, and they just showdetails, which are essential to the understanding of the invention,while other details are left out. Throughout, the same referencenumerals are used for identical or corresponding parts.

DETAILED DESCRIPTION OF THE INVENTION

Initially it may be convenient to define that, the term “distal end” ofthe disposable double pointed injection needle according to theinvention is meant to refer to the end 2 penetrating into the human body11, whereas the term “proximal end” is meant to refer to the oppositeend 3 entering into the cartridge 12.

FIGS. 1 and 2 shows the disposable double pointed injection needleaccording to the invention. The injection needle comprises of five mainparts: a needle cannula 1, a needle hub 4, a safety shield 10, aresilient element 21 and a container 13.

The needle cannula 1 is elongated and both ends 2, 3 are sharpenedusually by being cut in an oblique cut. The needle cannula 1 is firmlyfastened in a needle hub 4. The distal part of the needle cannula 1extending from the fastening point in the needle hub 4 is referred to asthe injection part 8, and the part extending in the proximal directionfrom its fastening point in the needle hub 4 is referred to as thecartridge part 9.

The needle hub 4, which is separately shown in FIG. 4, has a distal end5 and a proximal end 6. The proximal end 6 is on the interior surfaceprovided with a thread 7, which fits over an external thread on thecartridge 12 or on a not shown syringe carrying the cartridge 12. Inthis way the disposable double pointed injection needle can easily beconnected and disconnected to the cartridge 12 or the syringe carryingthe cartridge 12. The needle hub 4 can be provided with a not showncover covering the cartridge part 9 of the needle cannula 1. This notshown cover can be connected to the needle hub 4 by a hinge, such thatthe cover can be opened prior to connecting the needle hub 4 to asyringe, and closed when the needle hub 4 has been disconnected from asyringe.

The needle hub 4 has at the distal end 5 a centrally located hub tower15 surrounded by a circular well 14 through which a channel 16 reachingall the way through the needle hub 4 to the proximal end 6 is formed.The needle cannula 1 is under manufacturing placed in this channel 16,and the channel is filled with glue or other material, which can firmlyfasten the needle cannula 1 to the needle hub 4. The glue used coulde.g. be ordinary glue for gluing metal to a polymeric material, or itcould be glue which is harden by use of UV light. Instead of using glue,the material of the hub 4 could be melted to fasten the needle cannula 1to the hub 4. The height of the hub tower 15 and the length of thechannel 16 can vary depending on the type of the disposable doublepointed injection needle. A longer channel 16 gives a better controlover the sideways movements of the needle cannula 1 duringmanufacturing. If wanted the hub tower 15 can have a height such thatthe distal end of the hub tower 15 aligns the distal top surface 17 ofthe needle hub 4. The depth of the well 14 is chosen such that the well14 can support a resilient element in the form of a helical spring 21which is located between the needle hub 4 and the safety shield 10pressing the safety shield 10 away from the needle hub 4.

The needle hub 4 is on the outside surface provided with a number oftracks 18 into which tracks 18 a number of projections 22 located on thesafety shield 10 fits. At the proximal end 6, the needle hub 4 isprovided with a number of outward pointing ribs 19, which interacts witha number of inwardly pointing ribs 20 located on the inside surface ofthe container 13.

The safety shield 10, which is shown in FIG. 3 is guided on the outsidesurface of the needle hub 4 as shown in FIG. 2. The safety shield 10 ison the inside surface provided with a number of inwardly pointingprojections 22. Each of these projections 22 can, as shown, be carriedon a resilient arm 23 formed as an integral part of the safety shield10. The projections 22 can however be moulded directly on the insidesurface of the safety shield in which case they would not be visiblefrom outside the safety shield 10, as shown in FIG. 7 and FIG. 8. Thesafety shield 10 is formed as a cup or a hat and closed on all sidesexcept the proximal side, which fits over the needle hub 4. At thedistal end, the safety shield 10 is provided with a bore 25 large enoughfor the needle cannula 1 to pass through.

When the safety shield 10 is located on the needle hub 4 and thedisposable double pointed injection needle is in its initial position,the skin-piercing end 2 of the needle cannula 1 could be located alittle above the safety shield 10 as shown in FIG. 2. Prior to eachinjection, the user must perform a so-called airshot in order to pressany air contained in the cartridge 12 out through the needle cannula 1.When doing this, it is somewhat important that the user can visibleinspect that all the air is pressed out and only fluent medicine isexpelled from the needle cannula 1. Due to this the skin-piercing end 2of the needle cannula 1 must be visible. One way of making theskin-piercing end 2 of the needle cannula 1 visible is by making theneedle cannula 1 long enough to extend a little beyond the safety shield10, although having the skin-piercing end 2 of the needle cannula 1align the top surface of the safety shield 10 would be sufficient.Another solution could be to make the needle cannula 1 short enough tobe within the boundaries of the safety shield 10 and make the safetyshield 10 transparent or partly transparent. Yet another solution couldbe to keep the needle cannula 1 short enough to be within the boundariesof the safety shield 10 and to cut away a fraction 26 of the top of thesafety shield 10 making the skin-piercing end 2 of the needle cannula 1partly visible, as indicated with dashed lines in FIG. 5.

The hub 4 is on the outside provided with a number of tracks 18, whichis best seen in FIG. 4 and in FIG. 6. Each track 18 has a first part 27being substantially parallel to the needle cannula 1 and open at the topsurface of the needle hub 4. A second part 28 of the track 18 isconnected to the first part 27 at an acute angle and extends in thedirection towards the distal end 5 of the needle hub 4. When the safetyshield 10 is mounted over the needle hub 4, the projection 22 is passedinto the first part 27 of the track 18. This first part 27 of the track18 is provided with an elevation 29 having a sloping front allowing theprojection 22 to pass over the elevation 29 and a step backsidepreventing the projection 22 from moving out of the track 18 oncelocated there.

If wanted the second part 28 of the track 18 could be the part parallelto the needle cannula 1, the first part 27 would then be connected tothe second part at an acute angle.

A certain degree of resiliency between the projections 22 and the tracks18 is desired. Such a resiliency can be obtained either by providing thesafety shield 10 with resilient arms 23 carrying the projections, or bymaking the bottom of the tracks 18 resilient e.g. by only connecting thebottom of the tracks 18 to the needle hub 4 in some areas.

During injection, as shown in FIG. 2, the safety shield 10 is pressedback against the force of the helical spring 21 by the skin of a humanbody 11. When the needle cannula 1 is fully inserted into thesubcutaneous layer of the human body, the projection 22 enters into thesecond part 28 of the track 18. The two parts 27, 28 of the track 18 isseparated from each other by yet an elevation 30, which elevation 30 hasa steep backside preventing the projection 22 form sliding back into thefirst part 27 of the track 18 once the projection 22 has entered intothe second part 28 of the track 18. When the needle cannula 1 is removedfrom the subcutaneous layer of the user, the projection 22 will slidealong the second part 28 of the track 18, and once the needle cannula 1is fully retracted from the user the projection 22 will drop into a holeor well 31 where it will be permanently locked.

While commencing the injection the projection 22 is located in the firstpart 27 of the track 18 between the first elevation 29 and the secondelevation 30, as indicated in FIG. 2, where the position of the track 18is indicated with dashed lines. The front of the second elevation 30 hasa sloping surface, which the projection 22 has to climb before enteringthe second part 28. The slope of this front is chosen such that the usermust overcome a certain force before the projection 22 reaches the topof the elevation. For people suffering from needle anxiety it ispreferred to locate the skin-piercing end 2 of the needle cannula 1 outof sight i.e. inside the boundaries of the safety shield 10, and tomaximize the force a user has to apply before the safety shield 10starts to move. Making the slope of the front of the second elevation 30steep can maximize this force. By doing so a certain force applied bythe user has to be build up before the safety shield 10 starts to move,the movement will then be rather sudden once the force is release, whichis done when the projection 22 has started to be lifted over theelevation 30. The sudden release of the build up force will result in avery rapid insertion of the skin-piercing end 2 of the needle cannula 1into the subcutaneous layer of the human body.

The most distal end of the safety shield 10 could be moulded with atextured outside surface in order to increase the friction between theskin of the human body and the surface of the safety shield 10 duringinjection.

When the injection needle is in the initial position ready to beinserted into the human body the safety shield 10 surrounds at least themajor part of the injection part 8 of the needle cannula 1, leaving onlythe tip of the skin piercing end 2 of the needle cannula 1 free to beinspected when an air-shot is performed, as shown in FIG. 2. Once theneedle cannula 1 is fully inserted into the human body, the major partof the injection part 8 is exposed to the human body. The only part ofthe injection part 8 of the needle cannula 1 not being exposed to thehuman body is the part lying between the fastening point in the needlehub 4 and the top surface of the safety shield 10. The length of thispart depends on the height of the hub tower 15 and the wall thickness ofthe top surface of the safety shield 10.

In order to provide the user with a clear visible indication that theinjection needle has been used, the safety shield 10 can be providedwith at least one transparent area 32, which in its simplest form couldbe a hole in the safety shield 10. Through this transparent area 32 theuser can see a first area 33 on the outside surface of the needle hub 4.Since the first part 27 of the tracks 18 is located at an acute angle tothe second part 28, the safety shield 10 will rotate somedegrees—depended upon the angle—relatively to the needle hub 4 when aninjection is performed. This rotation will bring the transparent area 32to a second area 34 also located on the outside surface of the needlehub 4.

If more than one transparent area 32 are provided, a correspondingnumbers of first areas 33 and second areas 34 can be provided, such thata first area 33 is visible through each transparent area 32 prior touse, and that a second area 34 is visible through each transparent area32 when the shield 10 is irreversible locked in the third position afteruse.

When the injection needle is in the initial position ready to beinserted into the human body, the projection 22 is located in the firstpart 27 of the track 18. In this position the first area 33 on theoutside surface of the hub 4 is visible through the transparent area 32of the safety shield 10. After the injection, the projection 22 islocated in the hole or well 31, and the transparent area 32 of thesafety shield 10 is dislocated such that the second area 34 is nowvisible through the transparent area 32.

Since the colour of the first area 33 indicates that the disposabledouble pointed injection needle is ready for use, this colour is usuallygreen, black, blue or white. The second area 34 indicating that thedisposable double pointed injection needle has been used will typicallybe red, orange or yellow. However it could be possible to indicate thatthe safety needle is in a potential unsafe position by colouring thefirst area 33 in a colour indicating danger, and henceforth colour thesecond area 34 in a colour indicating that the safety needle is in apotentially safe position. Instead of colouring the areas 33, 34 symbolsor letters indicating the state of the disposable double pointedinjection needle could be used. The colours, symbols or letters can beapplied to the outside surface of the needle hub using inks, coatings ormouldings. The areas 33, 34 could be moulded with a depressed ortextured surface in order to enhance the adherence of the colour.

The disposable double pointed injection needle is delivered ready to useeither in a sterile peel bag or in a container 13. The container 13fully houses the needle hub 4, the needle cannula 1, the helical spring21 and the safety shield 10 before use. The proximal end of thecontainer 13 constitutes a peripheral surface 24 onto which a not shownpealable barrier is fastened. The barrier could be a sheet made of paperor from a polymeric or metallic sheet, and is preferably glued, meltedor welded on to the surface 24. The barrier is impermeable by germs suchthat the inside of the container is kept sterile until the barrier isbroken. Although the barrier is impermeable to germs and the like, it ispossible to sterilize the interior of the sheath e.g. with steam.

The proximal end of the container 13 is on the inside surface providedwith a number of inwardly pointing ribs 20, which interacts with ssimilar number of outwardly pointing ribs 19 located on the proximal end6 of the needle hub 4. If the fastening mechanism located on the insidesurface of the needle hub 4 is a thread 7 as shown in FIG. 2, thisthread 7 has to be screwed onto the thread of the cartridge 12 or thenot shown syringe in order to connect these two parts. This is done byrotating the container 13 containing the disposable double pointedinjection needle. When the rotational force emerging when the container13 is rotated relatively to the cartridge 12 or the not shown syringe istransferred directly to the needle hub 4, the rotational force isprevented from damaging the tracks 18 and the projections 22.

Instead of delivering the disposable double pointed injection needle tothe consumer in a separate container, the safety shield 10 itself couldbe used as a sterile confinement simply by prolonging the safety shield10 in the proximal direction such that the safety shield 10 fullysurrounds the needle hub 4 when the safety shield 10 is in itsready-to-use position shown in FIG. 2. The proximal end of the safetyshield 10 would then have to be sealed by a pealable barrier, and thehole 25 through which the needle cannula 1 passes during injection wouldalso have to be sealed by a pealable barrier or by a drop a softmaterial which can be penetrated by the needle cannula 1 e.g. silicone.The resilient arms 23 carrying the projections 22 could then be madesuch that the surface of the safety shield 10 was not penetrated asshown in FIG. 7 and in FIG. 8.

Some preferred embodiments have been shown in the foregoing, but itshould be stressed that the invention is not limited to these, but maybe embodied in other ways within the subject matter defined in thefollowing claims.

What is claimed is:
 1. A safety injection needle assembly comprising: aninjection needle having an injection part with a first end sharpened forpiercing skin and a cartridge part having second end for inserting intoa medication holding cartridge of an injection device; a hub in whichthe injection needle is mounted; a slideable safety shield for coveringthe injection part of the needle, the shield being biased to slidetoward and to cover the first end when no external force is applied tothe shield; a lock for irreversibly locking the safety shield in itsnormally biased position covering the injection part, the lock beingactivated by sliding the shield from its normally biased position to aposition exposing the injection part during an injection; and a visualindicator indicating that the safety shield is locked in the normallybiased position.
 2. The double pointed injection needle assemblyaccording to claim 1, wherein the needle hub is provided with at leastone indicating area and the safety shield is provided with at least onetransparent area through which the indicating area(s) is visible whenthe safety shield has been irreversible locked in the normally biasedposition, thereby providing the user with a visual indication when thedisposable double pointed injection needle is in a potentially safeposition.
 3. The double point injection needle assembly according toclaim 2, wherein the hub further is provided with at least oneadditional indicating area that is visible through the transparentarea(s) when the injection part of the needle has not been used.
 4. Thedouble pointed injection needle assembly according to claim 1, whereinthe safety shield is provided with at least one indicating area and thatthe needle hub is provided with at least one transparent area throughwhich the indicating area(s) is visible when said safety shield has beenirreversible locked over the injection part of the needle, therebyproviding the user with a visual indication when said disposable doublepointed injection needle is in a potentially safe position.
 5. Thedouble pointed injection needle assembly according to claim 4, whereinthe safety shield further is provided with at least one additionalindicating area that is visible through the transparent areas when theneedle has not been used to perform an injection.
 6. The double pointedinjection needle assembly according to claim 3, wherein the indicatingareas and the additional indicating areas are provided with differentcolors.
 7. The double pointed injection needle assembly according toclaim 3, wherein the indicating areas and the additional indicatingareas are provided with different symbols.
 8. A safety injection needleassembly comprising: an elongated cannula having a distal end forinjecting a patient; a hub in which the cannula is mounted; a moveablesafety shield that moves relative to the cannula between a firstposition exposing the distal end and a second position covering thedistal end; the safety shield being biased toward the second position; alocking means for irreversibly locking the safety shield in the secondposition after the shield is initially moved from the second position tothe first position and then returned to the second position; and avisual indicator that shows when the shield is irreversibly locked inthe second position, thereby preventing re-use of the needle assembly toadminister a second injection after it has been already used toadminister a first injection.
 9. The safety needle assembly of claim 8,wherein the visual indicator shows a colored surface after the shield isirreversibly locked.
 10. The safety needle assembly of claim 8, whereinthe visual indicator shows a textured surface after the shield isirreversibly locked.
 11. The safety needle assembly of claim 8, whereinthe visual indicator shows a shaded surface after the shield isirreversibly locked.
 12. A disposable double pointed injection needlecomprising an elongated cannula having two sharp ends and an outsidediameter, said needle cannula being fastened in a needle hub having adistal end and a proximal end, said proximal end being provided with afastening mechanism for mounting said needle hub on to a syringe havinga cartridge, said needle cannula having an injection part and acartridge part, the cartridge part for inserting into a cartridge thatis covered by said needle hub, the injection part for entering into ahuman body during injection, the injection part having an overall lengthshort enough to secure subcutaneously injection and the cartridge parthaving an overall length long enough to extend into the interior of thecartridge when said injection needle is fastened onto said syringe,wherein: said injection needle further is provided with a movable safetyshield movable mounted relatively to said needle hub and which movablesafety shield surrounds at least most of the injection part of saidneedle cannula when said needle cannula is in an unused state, and saidsafety shield can be longitudinal moved relatively to said needlecannula, such that said safety shield is first moved in the proximaldirection when the injection part of the cannula is penetrated into thesubcutis layer of a human body, thereby exposing the major part of theinjection part to the human body, and automatically moved in the distaldirection by a resilient element located between said needle hub andsaid safety shield when the injection part of said cannula is removedfrom the subcutis layer of the human body, and said safety shield isirreversible locked in a locked safe position where the movable safetyshield covers the skin piercing end of the injection part of said needlecannula when the injection part of said cannula is fully removed fromthe subcutis layer of a human body, and said double pointed disposableinjection needle further is provided with means providing the user witha visual indication when said disposable double pointed injection needleis in the safe position.
 13. A disposable double pointed injectionneedle according to claim 12, wherein said needle hub is provided withat least one indicating area and said safety shield is provided with atleast one transparent area through which transparent areas theindicating areas is visible when said safety shield has been moved tothe irreversible locked position thereby providing the user with avisual indication when said disposable double pointed injection needleis in a potentially safe position.
 14. A disposable double pointedinjection needle according to claim 13, characterized in that, said hubfurther is provided with at least one additional indicating area whichis visible through the transparent areas when said needle cannula is inthe unused state.
 15. A disposable double pointed injection needleaccording to claim 13, characterized in that, said safety shield isprovided with at least one indicating area and that said needle hub isprovided with at least one transparent area through which transparentareas the indicating areas is visible when said safety shield has beenmoved to the irreversible locked position thereby providing the userwith a visual indication when said disposable double pointed injectionneedle is in a potentially safe position.
 16. A disposable doublepointed injection needle according to claim 15, characterized in that,said safety shield further is provided with at least one additionalindicating area which is visible through the transparent areas when saidneedle cannula is in the unused state.
 17. A disposable double pointedinjection needle according to claim 14, characterized in that, theindicating areas and the additional indicating areas are provided withdifferent colors, different symbols or different colors and differentsymbols.